Motor vehicles are commonly equipped with a window washer for spraying washer liquid onto the windshield for clearing the view of the windshield in cooperation with a windshield wiper. Typically, operation of a window washer is accompanied by the activation of a windshield wiper. For optimum utilization of the washer liquid of a limited supply, it is desirable to optimize the spray pattern of the washer liquid. There are two types of spray patterns. The first type consists of a linear spray pattern which permits a jet of washer liquid having a circular cross section to impinge upon a narrow region on the windshield. The second type consists of a sheet spray pattern which allows the washer liquid to impinge upon a wider region on the windshield.
It is known that the latter provides a superior window clearing performance over the former for a given consumption of the washer liquid and a given number of cycles of wiper operation. When the washer liquid is sprayed with a certain spread, the size of the water droplets in the central part of the washer liquid spray is typically larger than those in the peripheral part. Therefore, when the nozzles for the window washer are aimed to the central part of the windshield, the droplets of the washer liquids evenly land on the windshield when the vehicle is stationary. However, when the vehicle is traveling at high speed, a high speed air flow is produced along the surface of the windshield, and the small droplets of the washer liquid tend to be blown away without landing on the windshield. Therefore, according to such a conventional arrangement, a significant part of the washer liquid is flown above the windshield when the vehicle is traveling at high speed, and is hence wasted.
It is conceivable to lower the aim of the washer nozzles. It may improve the situation when the vehicle is traveling at high speed, but the washer liquid will land preferentially in the lower part of the windshield when the vehicle is either stationary or traveling at low speed. A significant part of the washer liquid may even hit below the lower edge of the windshield. Therefore, there has been a problem that the spray pattern of window washer nozzles cannot be optimized for all speed ranges of the vehicle.